The Institute of Electrical and Electronics Engineers (IEEE) 802 Committee is planning to develop technical standard for IEEE 802.16m, being technical standard that has been further advanced by one level than the current standard of mobile WiMAX, as the next generation standard of WiBro/mobile WiMAX. IEEE 802.16m has a transmission rate of 100 Mbps as a target upon moving, and has a transmission rate of 1 Gbps as a target upon fixing.
The wireless communication system based on IEEE 802.16m is using the Multi-Input Multi-Out (MIMO) scheme where a transmitting end including a plurality of antennas transmits different data through the respective antennas, for the enhancement in efficiency of data transmission. With the use of the MIMO scheme, a wireless communication system obtains a diversity gain and increases a data transmission rate.
In applying the MIMO scheme, transmission data is coded with a precoding matrix to transmit for enhancing the reliability of data transmission. IEEE 802.16m has proposed a method that selects a precoding matrix from a codebook on the basis of a subcarrier identifier (ID) in frequency domain, for determining a precoding matrix in the open-loop MIMO scheme.
However, since Channel State Information (CSI) is not fed back from a receiving end for selecting a precoding matrix unlike in the closed-loop MIMO scheme, the open-loop MIMO scheme cannot guarantee the performance enhancement of the wireless communication system when determining a precoding matrix according to the above-described method.
Moreover, in the open-loop MIMO scheme, when determining a precoding matrix according to the above-described method, a diversity gain is not obtained at a low-mobility communication environment because the precoding matrix is not changed for entire time, and consequently, the optimal precoding matrix cannot be determined.